Method and apparatus for transceiving wireless signal in wireless communication system

ABSTRACT

The present invention relates to a wireless communication system, specifically to a method comprising the steps of configuring a PCell of a licensed band and an SCell of an unlicensed band for a base station; receiving resource configuration information concerning the SCell by means of a physical downlink control channel (PDCCH) of the PCell; configuring a subframe set within a temporary time duration on the SCell on the basis of the resource configuration information; and communicating with the base station by means of the subframe set temporarily configured on the SCell, and to an apparatus for the method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/932,474, filed on Jul. 17, 2020, which is a continuation of U.S.patent application Ser. No. 16/248,400, filed on Jan. 15, 2019, now U.S.Pat. No. 10,743,302, which is a continuation of U.S. patent applicationSer. No. 15/329,572, filed on Jan. 26, 2017, now U.S. Pat. No.10,219,263, which is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2015/007879, filed on Jul. 28, 2015,which claims the benefit of U.S. Provisional Application No. 62/029,578,filed on Jul. 28, 2014, 62/031,838, filed on Jul. 31, 2014, 62/033,661,filed on Aug. 6, 2014, 62/058,682, filed on Oct. 2, 2014, 62/082,064,filed on Nov. 19, 2014 and 62/160,620, filed on May 13, 2015, thecontents of which are all hereby incorporated by reference herein intheir entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting/receivinga wireless signal. The wireless communication system includes a CA-based(Carrier Aggregation-based) wireless communication system.

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services including voice and dataservices. In general, a wireless communication system is a multipleaccess system that supports communication among multiple users bysharing available system resources (e.g. bandwidth, transmit power,etc.) among the multiple users. The multiple access system may adopt amultiple access scheme such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), or singlecarrier frequency division multiple access (SC-FDMA).

DISCLOSURE Technical Problem

It is an object of the present invention to provide a method andapparatus for efficiently performing operations of transmission andreception of a wireless signal.

Technical tasks obtainable from the present invention are non-limited bythe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

The object of the present invention can be achieved by providing amethod for performing communication by a terminal in a wirelesscommunication system, including configuring a primary cell (PCell) of alicensed band and a secondary cell (SCell) of an unlicensed band for abase station, receiving resource configuration information on the SCellthrough a Physical Downlink Control Channel (PDCCH) of the PCell,configuring a subframe set within a temporary time period on the SCellbased on the resource configuration information, and communicating withthe base station using the subframe set temporally configured on theSCell.

In another aspect of the present invention, provided herein is aterminal configured to perform communication in a wireless communicationsystem, the terminal including an radio frequency (RF) module, and aprocessor, wherein the processor is configured to configure a primarycell (PCell) of a licensed band and a secondary cell (SCell) of anunlicensed band for a base station, receive resource configurationinformation on the SCell through a Physical Downlink Control Channel(PDCCH) of the PCell, configure a subframe set within a temporary timeperiod on the SCell based on the resource configuration information, andcommunicate with the base station using the subframe set temporallyconfigured on the SCell.

Preferably, the subframe set may include only downlink subframes or onlyuplink subframes.

Preferably, the subframe set may include one or more uplink subframesand one or more downlink subframes arranged thereafter.

Preferably, a specific signal may be transmitted for a predeterminedtime after an end time of the one or more uplink subframes.

Preferably, a length of the temporary time period may be pre-indicatedthrough an Radio Resource Control (RRC) message, and a subframe patternin the subframe set may be indicated using the resource configurationinformation on the SCell.

Advantageous Effects

According to embodiments of the present invention, wireless signaltransmission and reception can be efficiently performed in a wirelesscommunication system.

Effects obtainable from the present invention are non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

FIG. 2 illustrates a radio frame structure.

FIG. 3 illustrates a resource grid of a downlink slot.

FIG. 4 illustrates a downlink subframe structure.

FIG. 5 illustrates an example of Enhanced Physical Downlink ControlChannel (EPDCCH).

FIG. 6 illustrates the structure of an uplink subframe.

FIG. 7 illustrates uplink-downlink frame timing relation.

FIG. 8 is a block diagram illustrating a transmitter and a receiver forOFDMA and SC-FDMA.

FIG. 9 illustrates a carrier aggregation (CA)-based wirelesscommunication system.

FIG. 10 illustrates a cross-carrier scheduling.

FIG. 11 illustrates carrier aggregation of a licensed band and anunlicensed band.

FIGS. 12 and 13 illustrate a method of occupying resources within alicensed band.

FIG. 14 illustrates a communication performing method according to anembodiment of the present invention.

FIG. 15 illustrates a base station and a user equipment applicable to anembodiment of the present invention.

BEST MODE

Embodiments of the present invention are applicable to a variety ofwireless access technologies such as code division multiple access(CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), and single carrier frequency division multiple access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, and EvolvedUTRA (E-UTRA). UTRA is a part of Universal Mobile TelecommunicationsSystem (UMTS). 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA,employing OFDMA for downlink and SC-FDMA for uplink. LTE-Advanced(LTE-A) evolves from 3GPP LTE.

While the following description is given, centering on 3GPP LTE/LTE-Afor clarity, this is purely exemplary and thus should not be construedas limiting the present invention. It should be noted that specificterms disclosed in the present invention are proposed for convenience ofdescription and better understanding of the present invention, and theuse of these specific terms may be changed to other formats within thetechnical scope or spirit of the present invention.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

When powered on or when a UE initially enters a cell, the UE performsinitial cell search involving synchronization with a BS in step S101.For initial cell search, the UE synchronizes with the BS and acquireinformation such as a cell Identifier (ID) by receiving a primarysynchronization channel (P-SCH) and a secondary synchronization channel(S-SCH) from the BS. Then the UE may receive broadcast information fromthe cell on a physical broadcast channel (PBCH). In the mean time, theUE may check a downlink channel status by receiving a downlink referencesignal (DL RS) during initial cell search.

After initial cell search, the UE may acquire more specific systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation of the PDCCH in step S102.

The UE may perform a random access procedure to access the BS in stepsS103 to S106. For random access, the UE may transmit a preamble to theBS on a physical random access channel (PRACH) (S103) and receive aresponse message for preamble on a PDCCH and a PDSCH corresponding tothe PDCCH (S104). In the case of contention-based random access, the UEmay perform a contention resolution procedure by further transmittingthe PRACH (S105) and receiving a PDCCH and a PDSCH corresponding to thePDCCH (S106).

After the foregoing procedure, the UE may receive a PDCCH/PDSCH (S107)and transmit a physical uplink shared channel (PUSCH)/physical uplinkcontrol channel (PUCCH) (S108), as a general downlink/uplink signaltransmission procedure. Control information transmitted from the UE tothe BS is referred to as uplink control information (UCI). The UCIincludes hybrid automatic repeat and requestacknowledgement/negative-acknowledgement (HARQ-ACK/NACK), schedulingrequest (SR), channel state information (CSI), etc. The CSI includes achannel quality indicator (CQI), a precoding matrix indicator (PMI), arank indicator (RI), etc. While the UCI is transmitted on a PUCCH ingeneral, the UCI may be transmitted on a PUSCH when control informationand traffic data need to be simultaneously transmitted. In addition, theUCI may be aperiodically transmitted through a PUSCH according torequest/command of a network.

FIG. 2 illustrates a radio frame structure. Uplink/downlink data packettransmission is performed on a subframe-by-subframe basis. A subframe isdefined as a predetermined time interval including a plurality ofsymbols. 3GPP LTE supports a type-1 radio frame structure applicable tofrequency division duplex (FDD) and a type-2 radio frame structureapplicable to time division duplex (TDD).

FIG. 2(a) illustrates a type-1 radio frame structure. A downlinksubframe includes 10 subframes each of which includes 2 slots in thetime domain. A time for transmitting a subframe is defined as atransmission time interval (TTI). For example, each subframe has aduration of 1 ms and each slot has a duration of 0.5 ms. A slot includesa plurality of OFDM symbols in the time domain and includes a pluralityof resource blocks (RBs) in the frequency domain. Since downlink usesOFDM in 3GPP LTE, an OFDM symbol represents a symbol period. The OFDMsymbol may be called an SC-FDMA symbol or symbol period. An RB as aresource allocation unit may include a plurality of consecutivesubcarriers in one slot.

The number of OFDM symbols included in one slot may depend on cyclicprefix (CP) configuration. CPs include an extended CP and a normal CP.When an OFDM symbol is configured with the normal CP, for example, thenumber of OFDM symbols included in one slot may be 7. When an OFDMsymbol is configured with the extended CP, the length of one OFDM symbolincreases, and thus the number of OFDM symbols included in one slot issmaller than that in case of the normal CP. In case of the extended CP,the number of OFDM symbols allocated to one slot may be 6. When achannel state is unstable, such as a case in which a UE moves at a highspeed, the extended CP can be used to reduce inter-symbol interference.

When the normal CP is used, one subframe includes 14 OFDM symbols sinceone slot has 7 OFDM symbols. The first three OFDM symbols at most ineach subframe can be allocated to a PDCCH and the remaining OFDM symbolscan be allocated to a PDSCH.

FIG. 2(b) illustrates a type-2 radio frame structure. The type-2 radioframe includes 2 half frames. Each half frame includes 4(5) normalsubframes and 10 special subframes. The normal subframes are used foruplink or downlink according to UL-DL configuration. A subframe iscomposed of 2 slots.

Table 1 shows subframe configurations in a radio frame according toUL-DL configurations.

TABLE 1 Uplink- Downlink-to- downlink Uplink Switch Subframe numberconfiguration point periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D SU U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D SU U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D6 5 ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes DwPTS(Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS (Uplink PilotTimeSlot). DwPTS is used for initial cell search, synchronization orchannel estimation in a UE and UpPTS is used for channel estimation in aBS and uplink transmission synchronization in a UE. The GP eliminates ULinterference caused by multi-path delay of a DL signal between a UL anda DL.

The radio frame structure is merely exemplary and the number ofsubframes included in the radio frame, the number of slots included in asubframe, and the number of symbols included in a slot can be vary.

FIG. 3 illustrates a resource grid of a downlink slot.

Referring to FIG. 3 , a downlink slot includes a plurality of OFDMsymbols in the time domain. While one downlink slot may include 7 OFDMsymbols and one resource block (RB) may include 12 subcarriers in thefrequency domain in the figure, the present invention is not limitedthereto. Each element on the resource grid is referred to as a resourceelement (RE). One RB includes 12×7 REs. The number NRB of RBs includedin the downlink slot depends on a downlink transmit bandwidth. Thestructure of an uplink slot may be same as that of the downlink slot.

FIG. 4 illustrates a downlink subframe structure.

Referring to FIG. 4 , a maximum of three (four) OFDM symbols located ina front portion of a first slot within a subframe correspond to acontrol region to which a control channel is allocated. The remainingOFDM symbols correspond to a data region to which a physical downlinkshared chancel (PDSCH) is allocated. A basic resource unit of the dataregion is an RB. Examples of downlink control channels used in LTEinclude a physical control format indicator channel (PCFICH), a physicaldownlink control channel (PDCCH), a physical hybrid ARQ indicatorchannel (PHICH), etc. The PCFICH is transmitted at a first OFDM symbolof a subframe and carries information regarding the number of OFDMsymbols used for transmission of control channels within the subframe.The PHICH is a response of uplink transmission and carries an HARQacknowledgment (ACK)/negative-acknowledgment (NACK) signal. Controlinformation transmitted through the PDCCH is referred to as downlinkcontrol information (DCI). The DCI includes uplink or downlinkscheduling information or an uplink transmit power control command foran arbitrary UE group.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). Formats 0, 3, 3A and 4 for uplinkand formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for downlink are definedas DCI formats. Information field type, the number of informationfields, the number of bits of each information field, etc. depend on DICformat. For example, the DCI formats selectively include informationsuch as hopping flag, RB assignment, MCS (Modulation Coding Scheme), RV(Redundancy Version), NDI (New Data Indicator), TPC (Transmit PowerControl), HARQ process number, PMI (Precoding Matrix Indicator)confirmation as necessary. Accordingly, the size of control informationmatched to a DCI format depends on the DCI format. A arbitrary DCIformat may be used to transmit two or more types of control information.For example, DIC formats 0/1A is used to carry DCI format 0 or DICformat 1, which are discriminated from each other using a flag field.

A PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, information on resourceallocation of an upper-layer control message such as a random accessresponse transmitted on the PDSCH, a set of Tx power control commands onindividual UEs within an arbitrary UE group, a Tx power control command,information on activation of a voice over IP (VoIP), etc. A plurality ofPDCCHs can be transmitted within a control region. The UE can monitorthe plurality of PDCCHs. The PDCCH is transmitted on an aggregation ofone or several consecutive control channel elements (CCEs). The CCE isalogical allocation unit used to provide the PDCCH with a coding ratebased on a state of a radio channel. The CCE corresponds to a pluralityof resource element groups (REGs). A format of the PDCCH and the numberof bits of the available PDCCH are determined by the number of CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging identifier (e.g.,paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is forsystem information (more specifically, a system information block(SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC.When the PDCCH is for a random access response, a random access-RNTI(RA-RNTI) may be masked to the CRC.

The PDCCH carries a message known as DCI which includes resourceassignment information and other control information for a UE or UEgroup. In general, a plurality of PDCCHs can be transmitted in asubframe. Each PDCCH is transmitted using one or more CCEs. Each CCEcorresponds to 9 sets of 4 REs. The 4 REs are referred to as an REG. 4QPSK symbols are mapped to one REG. REs allocated to a reference signalare not included in an REG, and thus the total number of REGs in OFDMsymbols depends on presence or absence of a cell-specific referencesignal. The concept of REG (i.e. group based mapping, each groupincluding 4 REs) is used for other downlink control channels (PCFICH andPHICH). That is, REG is used as a basic resource unit of a controlregion. 4 PDCCH formats are supported as shown in Table 2.

TABLE 2 PDCCH Number of CCEs Number Number of PDCCH format (n) of REGsbits 0 1 9 72 1 2 8 144 2 4 36 288 3 5 72 576

CCEs are sequentially numbered. To simplify a decoding process,transmission of a PDCCH having a format including n CCEs can be startedusing as many CCEs as a multiple of n. The number of CCEs used totransmit a specific PDCCH is determined by a BS according to channelcondition. For example, if a PDCCH is for a UE having a high-qualitydownlink channel (e.g. a channel close to the BS), only one CCE can beused for PDCCH transmission. However, for a UE having a poor channel(e.g. a channel close to a cell edge), 8 CCEs can be used for PDCCHtransmission in order to obtain sufficient robustness. In addition, apower level of the PDCCH can be controlled according to channelcondition.

LTE defines CCE positions in a limited set in which PDCCHs can bepositioned for each UE. CCE positions in a limited set that the UE needsto monitor in order to detect the PDCCH allocated thereto may bereferred to as a search space (SS). In LTE, the SS has a size dependingon PDCCH format. A UE-specific search space (USS) and a common searchspace (CSS) are separately defined. The USS is set per UE and the rangeof the CSS is signaled to all UEs. The USS and the CSS may overlap for agiven UE. In the case of a considerably small SS with respect to aspecific UE, when some CCEs positions are allocated in the SS, remainingCCEs are not present. Accordingly, the BS may not find CCE resources onwhich PDCCHs will be transmitted to available UEs within givensubframes. To minimize the possibility that this blocking continues tothe next subframe, a UE-specific hopping sequence is applied to thestarting point of the USS.

Table 3 shows sizes of the CSS and USS.

TABLE 3 Number Number of candidates Number of candidates PDCCH of CCEsin common search in dedicated search format (n) space space 0 1 — 6 1 2— 6 2 4 4 2 3 8 2 2

To control computational load of blind decoding based on the number ofblind decoding processes to an appropriate level, the UE is not requiredto simultaneously search for all defined DCI formats. In general, the UEsearches for formats 0 and 1A at all times in the USS. Formats 0 and 1Ahave the same size and are discriminated from each other by a flag in amessage. The UE may need to receive an additional format (e.g. format 1,1B or 2 according to PDSCH transmission mode set by a BS). The UEsearches for formats 1A and 1C in the CSS. Furthermore, the UE may beset to search for format 3 or 3A. Formats 3 and 3A have the same size asthat of formats 0 and 1A and may be discriminated from each other byscrambling CRC with different (common) identifiers rather than aUE-specific identifier. PDSCH transmission schemes and informationcontent of DCI formats according to transmission mode (TM) are arrangedbelow.

Transmission mode (TM)

-   -   Transmission mode 1: Transmission from a single base station        antenna port    -   Transmission mode 2: Transmit diversity    -   Transmission mode 3: Open-loop spatial multiplexing    -   Transmission mode 4: Closed-loop spatial multiplexing    -   Transmission mode 5: Multi-user MIMO (Multiple Input Multiple        Output)    -   Transmission mode 6: Closed-loop rank-1 precoding    -   Transmission mode 7: Single-antenna port (port 5) transmission    -   Transmission mode 8: Double layer transmission (ports 7 and 8)        or single-antenna port (port 7 or 8) transmission    -   Transmission mode 9: Transmission through up to 8 layers (ports        7 to 14) or single-antenna port (port 7 or 8) transmission

DCI format

-   -   Format 0: Resource grants for PUSCH transmission    -   Format 1: Resource assignments for single codeword PDSCH        transmission (transmission modes 1, 2 and 7)    -   Format 1A: Compact signaling of resource assignments for single        codeword PDSCH (all modes)    -   Format 1B: Compact resource assignments for PDSCH using rank-1        closed loop precoding (mod 6)    -   Format 1C: Very compact resource assignments for PDSCH (e.g.        paging/broadcast system information)    -   Format 1D: Compact resource assignments for PDSCH using        multi-user MIMO (mode 5)    -   Format 2: Resource assignments for PDSCH for closed-loop MIMO        operation (mode 4)    -   Format 2A: Resource assignments for PDSCH for open-loop MIMO        operation (mode 3)    -   Format 3/3A: Power control commands for PUCCH and PUSCH with        2-bit/1-bit power adjustments

FIG. 5 illustrates an EPDCCH. The EPDCCH is a channel additionallyintroduced in LTE-A.

Referring to FIG. 5 , a PDCCH (for convenience, legacy PDCCH or L-PDCCH)according to legacy LTE may be allocated to a control region (see FIG. 4) of a subframe. In the figure, the L-PDCCH region means a region towhich a legacy PDCCH may be allocated. Meanwhile, a PDCCH may be furtherallocated to the data region (e.g., a resource region for a PDSCH). APDCCH allocated to the data region is referred to as an E-PDCCH. Asshown, control channel resources may be further acquired via the E-PDCCHto mitigate a scheduling restriction due to restricted control channelresources of the L-PDCCH region. Similarly to the L-PDCCH, the E-PDCCHcarries DCI. For example, the E-PDCCH may carry downlink schedulinginformation and uplink scheduling information. For example, the UE mayreceive the E-PDCCH and receive data/control information via a PDSCHcorresponding to the E-PDCCH. In addition, the UE may receive theE-PDCCH and transmit data/control information via a PUSCH correspondingto the E-PDCCH. The E-PDCCH/PDSCH may be allocated starting from a firstOFDM symbol of the subframe, according to cell type. In thisspecification, the PDCCH includes both L-PDCCH and EPDCCH unlessotherwise noted.

FIG. 6 illustrates an uplink subframe structure.

Referring to FIG. 6 , an uplink subframe includes a plurality of (e.g.2) slots. A slot may include different numbers of SC-FDMA symbolsaccording to CP lengths. For example, a slot may include 7 SC-FDMAsymbols in a normal CP case. The uplink subframe is divided into acontrol region and a data region in the frequency domain. The dataregion is allocated with a PUSCH and used to carry a data signal such asaudio data. The control region is allocated a PUCCH and used to carrycontrol information. The PUCCH includes an RB pair (e.g. m=0, 1, 2, 3)located at both ends of the data region in the frequency domain andhopped in a slot boundary. Control information includes HARQ ACK/NACK,CQI, PMI, RI, etc.

FIG. 7 illustrates uplink-downlink frame timing relation.

Referring to FIG. 7 , transmission of the uplink radio frame number istarts prior to (N_(TA)+N_(TAoffset))*T_(s) seconds from the start ofthe corresponding downlink radio frame. In case of the LTE system,0<N_(TA)<20512, N_(TAoffset)=0 in FDD, and N_(TAoffset)=624 in TDD. Thevalue N_(Taoffset) is a value in advance recognized by the BS and theUE. If N_(TA) is indicated through a timing advance command during arandom access procedure, the UE adjusts transmission timing of UL signal(e.g., PUCCH/PUSCH/SRS) through the above equation. UL transmissiontiming is set to multiples of 16 T_(s). The timing advance commandindicates the change of the UL timing based on the current UL timing.The timing advance command T_(A) within the random access response is a11-bit timing advance command, and indicates values of 0, 1, 2, . . . ,1282 and a timing adjustment value is given by N_(TA)=T_(A)*16. In othercases, the timing advance command T_(A) is a 6-bit timing advancecommand, and indicates values of 0, 1, 2, . . . , 63 and a timingadjustment value is given by N_(TA,new)=N_(TA,old)+(T_(A)−31)*16. Thetiming advance command received at subframe n is applied from thebeginning of subframe n+6. In case of FDD, as shown, transmitting timingof UL subframe n is advanced based on the start time of the DL subframen. On the contrary, in case of TDD, transmitting timing of UL subframe nis advanced based on the end time of the DL subframe n+1 (not shown).

FIG. 8 is a block diagram illustrating a transmitter and a receiver forOFDMA and SC-FDMA. In uplink (UL), a transmitter may be a part of a UserEquipment (UE) and a receiver may be a part of a Base Station (BS). Indownlink (DL), the transmitter may be a part of the BS and the receivermay be a part of the UE.

Referring to FIG. 1 , an OFDMA transmitter includes a serial-to-parallelconverter 202, a subcarrier mapping module 206, an M-point InverseDiscrete Fourier Transform (IDFT) module 208, a Cyclic Prefix (CP)attachment module 212, a parallel-to-serial converter 210, and a RadioFrequency (RF)/Digital-to-Analog Converter (DAC) module 214.

Signal processing in the OFDMA transmitter is as follows. First, abitstream is modulated into a data symbol sequence. The bitstream may beobtained by performing various types of signal processing includingchannel encoding, interleaving, and scrambling of a data block deliveredfrom a Medium Access Control (MAC) layer. The bitstream is also referredto as a codeword and is equivalent to a data block received from the MAClayer. The data block received from the MAC layer is referred to as atransport block as well. A modulation scheme may include, but is notlimited to, Binary Phase Shift Keying (BPSK), Quadrature Phase ShiftKeying (QPSK), and n-Quadrature Amplitude Modulation (n-QAM). Next, aserial data symbol sequence is converted into data symbols N by N inparallel (202). The N data symbols are mapped to N subcarriers allocatedamong a total of M subcarriers and the (M-N) remaining subcarriers arepadded with 0s (206). The data symbol mapped in a frequency domain isconverted to a time-domain sequence through M-point IDFT processing(208). Thereafter, in order to reduce Inter-Symbol Interference (ISI)and Inter-Carrier Interference (ICI), an OFDMA symbol is generated byattaching a CP to the time-domain sequence (212). The generated parallelOFDMA symbol is converted into a serial OFDMA symbol (210). The OFDMAsymbol is then transmitted to a receiver through digital-to-analogconversion, frequency upconversion, and the like (214). Availablesubcarriers among the (M-N) remaining subcarriers are allocated toanother user. Meanwhile, an OFDMA receiver includes anRF/Analog-to-Digital Converter (ADC) module 216, a serial-to-parallelconverter 218, a CP removal module 222, an M-point Discrete FourierTransform (DFT) module 224, a subcarrier demapping/equalization module226, a parallel-to-serial converter 230, and a detection module. Asignal processing process of the OFDMA receiver has a configurationopposite to that of the OFDMA transmitter.

Meanwhile, compared to the OFDMA transmitter, an SC-FDMA transmitterfurther includes an N-point DFT module 204 before the subcarrier mappingmodule 206. The SC-FDMA transmitter spreads a plurality of data in afrequency domain through DFT prior to IDFT processing, therebyconsiderably decreasing a Peak-to-Average Power Ratio (PAPR) of atransmission signal in comparison with an OFDMA scheme. Compared to theOFDMA receiver, an SC-FDMA receiver further includes an N-point IDFTmodule 226 after the subcarrier demapping module 226. A signalprocessing process of the SC-FDMA receiver has configuration opposite tothat of the SC-FDMA transmitter.

FIG. 9 illustrates carrier aggregation (CA) communication system.

Referring to FIG. 9 , a plurality of UL/DL component carriers (CCs) canbe aggregated to support a wider UL/DL bandwidth. The CCs may becontiguous or non-contiguous in the frequency domain. Bandwidths of theCCs can be independently determined. Asymmetrical CA in which the numberof UL CCs is different from the number of DL CCs can be implemented.Control information may be transmitted/received only through a specificCC. This specific CC may be referred to as a primary CC and other CCsmay be referred to as secondary CCs. For example, when cross-carrierscheduling (or cross-CC scheduling) is applied, a PDCCH for downlinkallocation can be transmitted on DL CC #0 and a PDSCH correspondingthereto can be transmitted on DL CC #2. The term “component carrier” maybe replaced by other equivalent terms (e.g. “carrier”, “cell”, etc.).

For cross-CC scheduling, a carrier indicator field (CIF) is used.Presence or absence of the CIF in a PDCCH can be determined by higherlayer signaling (e.g. RRC signaling) semi-statically and UE-specifically(or UE group-specifically). The baseline of PDCCH transmission issummarized as follows.

-   -   CIF disabled: a PDCCH on a DL CC is used to allocate a PDSCH        resource on the same DL CC or a PUSCH resource on a linked UL        CC.        -   No CIF    -   CIF enabled: a PDCCH on a DL CC can be used to allocate a PDSCH        or PUSCH resource on a specific DL/UL CC from among a plurality        of aggregated DL/UL CCs using the CIF.    -   LTE DCI format extended to have CIF    -   CIF corresponds to a fixed x-bit field (e.g. x=3) (when CIF is        set)    -   CIF position is fixed irrespective of DIC format size (when CIF        is set)

When the CIF is present, the BS may allocate a monitoring DL CC (set) toreduce BD complexity of the UE. For PDSCH/PUSCH scheduling, the UE maydetect/decode a PDCCH only on the corresponding DL CCs. The BS maytransmit the PDCCH only through the monitoring DL CC (set). Themonitoring DL CC set may be set UE-specifically, UE-group-specificallyor cell-specifically.

FIG. 10 illustrates scheduling when a plurality of carriers isaggregated. It is assumed that 3 DL CCs are aggregated and DL CC A isset to a PDCCH CC. DL CC A˜C may be referred to as a serving CC, servingcarrier, serving cell, etc. When the CIF is disabled, each DL CC cantransmit only a PDCCH that schedules a PDSCH corresponding to the DL CCwithout a CIF according to LTE PDCCH rule (non-cross-CC scheduling).When the CIF is enabled through UE-specific (or UE-group-specific orcell-specific) higher layer signaling, a specific CC (e.g. DL CC A) cantransmit not only the PDCCH that schedules the PDSCH of DL CC A but alsoPDCCHs that schedule PDSCHs of other DL CCs using the CIF(cross-scheduling). A PDCCH is not transmitted on DL CC B and DL CC C.

Embodiment: Transceiving Signals in LTE-U

As more and more telecommunication devices require greater communicationcapacity, efficient utilization of limited frequency bands in futurewireless communication systems is increasingly important. Basically, thefrequency spectrum is divided into a licensed band and an unlicensedband. The licensed band includes frequency bands reserved for specificuses. For example, the licensed band includes government allocatedfrequency bands for cellular communication (e.g., LTE frequency bands).The unlicensed band is a frequency band reserved for public use and isalso referred to as a license-free band. The unlicensed band may be usedby anyone without permission or declaration so long as such use meetsradio regulations. The unlicensed band is distributed or designated foruse by anyone at a close distance, such as within a specific area orbuilding, in an output range that does not interfere with thecommunication of other wireless stations, and is widely used forwireless remote control, wireless power transmission, Wi-Fi, and thelike.

Cellular communication systems such as LTE systems are also exploringways to utilize unlicensed bands (e.g., the 2.4 GHz band and the 5 GHzband), used in legacy Wi-Fi systems, for traffic off-loading. Basically,since it is assumed that wireless transmission and reception isperformed through contention between communication nodes, it is requiredthat each communication node perform channel sensing (CS) beforetransmitting a signal and confirm that none of the other communicationnodes transmit a signal. This operation is referred to as clear channelassessment (CCA), and an eNB or a UE of the LTE system may also need toperform CCA for signal transmission in an unlicensed band. Forsimplicity, the unlicensed band used in the LTE-A system is referred toas the LTE-U band. In addition, when an eNB or UE of the LTE systemtransmits a signal, other communication nodes such as Wi-Fi should alsoperform CCA in order not to cause interference. For example, in the801.11ac Wi-Fi standard, the CCA threshold is specified to be −62 dBmfor non-Wi-Fi signals and −82 dBm for Wi-Fi signals. Accordingly, thestation (STA)/access point (AP) does not perform signal transmission soas not to cause interference when a signal other than Wi-Fi signals arereceived at a power greater than or equal to −62 dBm. In a Wi-Fi system,the STA or AP may perform CCA and signal transmission if a signal abovea CCA threshold is not detected for more than 4 μs.

FIG. 11 illustrates carrier aggregation of a licensed band and anunlicensed band. Referring to FIG. 11 , an eNB may transmit a signal toa UE or the UE may transmit a signal to the eNB in a situation ofcarrier aggregation of the licensed band (hereinafter, LTE-A band) andthe unlicensed band (hereinafter, LTE-U band). Here, the center carrieror frequency resource of the license band may be interpreted as a PCC orPCell, and the center carrier or frequency resource of the unlicensedband may be interpreted as an SCC or SCell.

FIGS. 12 and 13 illustrate a method of occupying resources within alicensed band. In order to perform communication between an eNB and a UEin an LTE-U band, the band should be occupied/secured for a specifictime period through contention with other communication systems (e.g.,Wi-Fi) unrelated to LTE-A. For simplicity, the time periodoccupied/secured for cellular communication in the LTE-U band isreferred to as a reserved resource period (RRP). There are variousmethods for securing the RRP interval. For example, a specificreservation signal may be transmitted such that other communicationsystem devices such as Wi-Fi can recognize that the correspondingwireless channel is busy. For example, the eNB may continuously transmitan RS and data signal such that a signal having a specific power levelor higher is continuously transmitted during the RRP interval. If theeNB has predetermined the RRP interval to occupy in the LTE-U band, theeNB may pre-inform the UE of the RRP interval to allow the UE tomaintain the communication transmission/reception link during theindicated RRP interval. The RRP interval information may be transmittedto the UE through another CC (e.g., the LTE-A band) connected throughcarrier aggregation.

For example, an RRP interval consisting of M consecutive subframes (SF)may be configured. Alternatively, one RRP interval may be configured asa set of non-consecutive SFs (not shown). Here, the eNB may pre-informthe UE through higher layer signaling (e.g., RRC or MAC signaling) or aphysical control/data channel of the value of M and the usage of the MSFs (using PCell). The start time of the RRP interval may be setperiodically by higher layer signaling (e.g., RRC or MAC signaling).Alternatively, the start time of the RRP interval may be specifiedthrough physical layer signaling (e.g., (E)PDCCH) in SF #n or SF # (n-k)when the start time of the RRP interval needs to be set to SF #n. Here,k is a positive integer (e.g., 4).

The RRP may be configured such that the SF boundary and the SFnumber/index thereof are aligned with the PCell (FIG. 2 ) (hereinafter,“aligned-RRP”), or configured to support the format in which the SFboundary or the SF number/index is not aligned with the PCell(hereinafter, “floating-RRP”) (FIG. 13 ). In the present invention, theSF boundaries being aligned between cells may mean that the intervalbetween SF boundaries of two different cells is shorter than or equal toa specific time (e.g., CP length or X μs (X≥0)). In addition, in thepresent invention, a PCell may refer to a cell that is referenced inorder to determine the SF (and/or symbol) boundary of a UCell in termsof time (and/or frequency) synchronization.

As another example of operation in the unlicensed band performed in acontention-based random access scheme, the eNB may perform carriersensing before data transmission/reception. If a current channel statusof the SCell is determined as being an idle when the channel status ischecked for whether it is busy or idle, the eNB may transmit ascheduling grant (e.g., (E)PDCCH) through the PCell (LTE-A band) or theSCell (LTE-U band), and attempt to perform data transmission/receptionon the SCell.

Hereinafter, a method for configuring a resource interval in acell/carrier in which available resource intervals arereserved/configured aperiodically or non-consecutively, and acorresponding operation of the eNB/UE are proposed. The presentinvention is applicable to an LTE-U system operating opportunisticallyin an unlicensed band based on carrier sensing. For simplicity, CAbetween a PCell operating in the existing licensed band and an SCelloperating in the LTE-U scheme is considered. For simplicity, theLTE-U-based cell (e.g., SCell) is defined as a UCell, and a resourceinterval reserved/configured aperiodically in the UCell is defined as anRRP. The center frequency of the UCell is defined as a (DL/UL) UCC.Cells (e.g., PCell, SCell) operating in the existing licensed band aredefined as LCells, and the center frequency of an LCell is defined as a(DL/UL) LCC.

Hereinafter, the transmission period and configuration information ofthe DCI (hereinafter, referred to as RRP-cfg DCI) signaled for thepurpose of RRP configuration in the situation of CA including theRRP-based UCell, and a method for determining an RRP start SF(number/index) in the UCell, and UE operation according to the SFconfiguration of the RRP and the RRP-cfg DCI transmission will bedescribed. For simplicity, a case in which a UCell is scheduled from thesame cell and a case in which a UCell is scheduled from another cell(e.g., PCell) are referred to as self-CC scheduling and cross-CCscheduling, respectively.

For simplicity, it is assumed that one licensed band and one unlicensedband are merged for a UE, and wireless communication is performedthrough the same. However, the proposed schemes of the present inventionmay also be applied to a situation wherein a plurality of licensed bandsand a plurality of unlicensed bands are used for carrier aggregation.The proposed schemes may also be applied to a case where signaltransmission/reception is performed between an eNB and a UE only in anunlicensed band. In addition, the proposed schemes of the presentinvention may be applied not only to the 3GPP LTE system but also tosystems having other characteristics. Hereinafter, the base station isused as a comprehensive term including a remote radio head (RRH), aneNB, a transmission point (TP), a reception point (RP), and a relay.

(0) Definition of RRP on UCell

RRP refers to a resource that is configurednon-consecutively/aperiodically depending on the result of carriersensing. In terms of UE operation and assumptions, the RRP may bedefined as follows:

1) a period during which the UE performs (time/frequency)synchronization for a UCell, or a synchronization signal (e.g., PSS,SSS) for the same is assumed to be transmitted (from the eNB);

2) a period during which a UE performs channel state measurement on aUCell or a reference signal (e.g., a cell-specific reference signal(CRS) or a channel state information reference signal (CSI-RS)) isassumed to be transmitted;

3) a period during which the UE performs (DL/UL grant) DCI detection inor for the UCell;

4) a period during which all or some of these operations/assumptions areimplemented in the UCell, considering the interval during which the UEperforms a (temporary) buffering operation to a signal received in theUCell.

(1) Transmission and configuration of RRP configuration DCI

The DCI or information/parameter (e.g., RRP-cfg DCI) transmitted for RRPconfiguration may be transmitted in the PDCCH format using CSS resourceson the PCell or may be transmitted through a specific signal (e.g., aradio channel reservation signal or preamble signal) configured on theUCell. The following two RRP-cfg DCI detection schemes may be considereddepending on the eNB's resource use frequency and/or scheduling plan forthe UCell (from the UE perspective).

-   -   Alt D1: Performing RRP-cfg DCI detection in all DL SFs

The UE may perform a detection operation for RRP-cfg DCI in all DL SFsof the PCell. One RRP-cfg DCI may be configured as a single PDCCHtransmitted through one DL SF, or a plurality of PDCCHs repeatedlytransmitted through R (>1) DL SFs.

-   -   Alt D2: Performing RRP-cfg DCI detection every N SFs

The UE may perform a detection of RRP-cfg DCI for one or M (>1) SFsevery N (>1) SFs. One RRP-cfg DCI may be transmitted (repeated) throughone or R (>1) SFs. Here, M may be set to the same value as R or amultiple of R, and the interval of R SFs configured for one RRP-cfg DCImay be allocated only in one interval of M SFs in which RRP-cfg DCIdetection is performed (i.e., not configured over a plurality ofintervals of M SFs).

Meanwhile, one RRP-cfg DCI may include RRP interval configurationinformation for a plurality of UCells. Specifically, each of a pluralityof fields (for simplicity, R-field) in the DCI may signal RRPconfiguration information for an individual/independent UCell. In thiscase, the RRP-cfg DCI may be transmitted in the form of a UE-commonRNTI-based PDCCH. That is, the RRP configuration information for aspecific UCell may be signaled through a combination of a specific RNTIand an R-field. For a UCell for which an RRP interval is not configured,information corresponding to “no RRP configuration” may be signaledthrough a corresponding R-field.

Alternatively, one RRP-cfg DCI may include RRP interval configurationinformation (on a specific UCell) for a plurality of UEs. Specifically,each of a plurality of fields (for simplicity, R-field) may signal RRPconfiguration information about one individual/independent UE. In thiscase, the RRP-cfg DCI may be transmitted in the form of a UE-commonRNTI-based PDCCH. That is, the RRP configuration information for aspecific UCell may be signaled through a combination of a specific RNTIand an R-field. For a UE for which an RRP interval is not configured,information corresponding to “no RRP configuration” may be signaledthrough the corresponding R-field for a UE.

Meanwhile, when RRP is defined as a valid CSI (reference/measurement)resource interval on the UCell, a UE configured with a specifictransmission mode (TM) may consider/assume that only RS transmissioncorresponding to the specific TM is performed in the interval set to theRRP. For example, if the UE is set to TM 2 or 4, it may operateassuming/considering only CRS transmission. If the UE is set to TM 9 or10, it may operate assuming/considering only the CSI-RS and/or CSI-IM(interference measurement) transmission.

The information signaled through the RRP-cfg DCI may include thefollowing information depending on the RRP-cfg DCItransmission/detection SF configuration (e.g., Alt D1 or Alt D2) and theSF resource configuration on the UCell (e.g., aligned-RRP orfloating-RRP).

RRP Interval Length and SF Usage

RRP-cfg DCI may be signaled for purposes of announcing the total time ofthe RRP interval (e.g., the total number of SFs in the RRP interval) andthe usage of SFs that constitute the RRP (e.g., whether the SFs are DLSFs or UL SFs). In order to prevent the RRP interval from beingdetermined to be idle through carrier sensing by other systems, the SFswithin one RRP interval may all be configured as DL SFs or UL SFs(without DL/UL switching interval). Alternatively, in the case of DL toUL switching, a guard period may exist (as in the TDD special SF) andthe aforementioned problem may be raised. On the other hand, in the caseof UL to DL switching, since the eNB may perform DL signal transmissionimmediately after receiving a UL signal from the UE, the SFs within oneRRP interval may be arranged in such a manner that consecutive UL SFsare arranged first and then consecutive DL SFs are arranged. Forexample, when one RRP interval consists of 4 SFs, the SFs in the RRP maybe arranged in a manner of UL/DL/DL/DL, UL/UL/DL/DL, or UL/UL/UL/DL. Forsimplicity, the proposed DL/UL combination is referred to as “UL-DLmixed RRP”. On the basis of this, the SFs in an RRP interval may beconfigured as 1) either (i) all DL SFs or (ii) the proposed combinationof DL SFs/UL SFs, 2) (i) all UL SFs or (ii) the proposed combination ofDL SFs/UL SFs, or 3) (i) all DL SFs or all UL SFs or (ii) the proposedcombination of DL SFs/UL SFs.

Alternatively, only the usage of the RRP configuration SF may beindicated through the RRP-cfg DCI while the length of the RRP intervalis preconfigured through the higher layer (e.g. RRC) signaling, or onlythe length of the RRP interval may be indicated through the RRP-cfg DCIwhile the usage of the RRP configuration SF is preconfigured through thehigher layer signaling.

Only the cross-CC scheduling may be allowed for the UCell when all theSFs in the RRP interval are configured as UL SFs or this configurationis included. In the case of HARQ timing (e.g., UL grant/PUSCH/PHICHtransmission) for the UL HARQ process/operation accompanying UL datatransmission/scheduling in a UCell, the following UL HARQ timing appliedto the FDD SCell may be applied to the UCell (depending on whether thePCell is in FDD or TDD) under assumption that the UCell is considered tobe identical to an FDD SCell. In terms of UL HARQ timing, the PCell maymean a cell configured to perform (cross-CC) scheduling on the UCell.

-   -   In case of FDD PCell: The UL grant scheduling PUSCH transmission        in SF #n is transmitted/received through SF #(n−4), and a PHICH        corresponding to the PUSCH transmission in SF #n is        transmitted/received through SF #(n+4).    -   In case of TDD PCell: The UL grant scheduling PUSCH transmission        in SF #n is transmitted/received through SF #(n−4), and a PHICH        corresponding to the PUSCH transmission in SF #n is        transmitted/received through SF #(n+6) (or UL HARQ timing        defined in the UL/DL configuration of the PCell is applied)

Even in the case of the UL-DL mixed RRP, there may exist the UL-to-DLswitching period (i.e., an RX-to-TX switching gap in the eNB).Accordingly, in order to perform stable DL transmission/schedulingduring the corresponding RRP, it may be necessary (for the LTE-U system)to continuously occupy the radio channel on the UCell during theRX-to-TX gap. To this end, a UE transmitting or configured/scheduled totransmit a UL channel/signal (e.g., PUSCH or SRS) through the last UL SFof the UL-DL mixed RRP (immediately before the first DL SF) may bedesignated/instructed to transmit a specific signal (hereinafter,referred to as a post-reservation signal) having a short duration fromthe end of the UL SF to a specific point in time (without carriersensing). The post-reservation signal may be configured in the form ofthe cyclic prefix (part thereof) or a cyclic postfix. The cyclic postfixis configured by a part copying the first part of the IFFT (IDFT of FIG.8 )-processed time-domain signal. The transmission related information(e.g., timing, duration) about the post-reservation signal may beconfigured by the eNB. In addition, even if UL channel/signaltransmission is not configured/scheduled in a given UL-DL mixed RRP (orthe last UL SF in the corresponding RRP), the UE may bedesignated/instructed to perform only transmission of a post-reservationsignal (from the end of the last UL SF without carrier sensing).

If a specific UE (e.g., a UE for which a TA value applied to ULtransmission is set to be very small) transmits the post reservationsignal until after the last UL SF within the UL-DL mixed RRP, the UE maynot properly receive the first OFDMA symbol in the first DL SF due tothe UL-to-DL switching operation, namely, the TX-to-RX switchingoperation (a gap accompanying the same). In consideration of this, 1)only UEs whose TA value is above a specific threshold value are allowedto perform transmission of a corresponding post-reservation signal, 2)whether or not to perform post-reservation signal transmission may beUE-specifically announced through RRC or UL grant, or 3) a UEexperiencing such a problem may be allowed to perform an operation forexcluding the first DL OFDMA symbol from the received signal (e.g.,puncturing the first DL OFDMA symbol). In addition, in consideration ofthe above-described problem, the UE-common signal/resource (e.g.,synchronization/reference signal and/or measurement signal/resource)transmitted through the first (or all) DL SFs in the UL-DL mixed RRP mayconsist only of OFDMA symbols that follow the first symbol. Otherwise, aUE-common signal/resource (e.g., a synchronization/reference signaland/or a measurement signal/resource, etc.) may also be present in thefirst OFDMA symbol. The proposed method is not limited to the UL-DLmixed RRP but may be applied to any RRP including UL-to-DL switching. Inthis case, the last UL SF and the first DL SF in the UL-DL mixed RRP maybe replaced with/considered as the UL SF located immediately before theUL SF and the DL SF located immediately after the UL SF, respectively.

The Number of Remaining SFs in RRP Interval

This information may be signaled to indicate the number of remaining SFs(or a parameter from which the number may be inferred, for example, theposition of the SF corresponding to the time point within the RRPinterval) in the remaining RRP interval from the time when the RRP-cfgDCI is detected (or the time corresponding to the detection time plus aspecific SF offset). This information may be useful in a situation whereRRP-cfg DCI transmission/detection is set to be performed for all DL SFsas in the case of Alt D1).

RRP Start SF Number/Index

This information may be signaled to indicate an SF number/index of thestart SF of the RRP interval (or a parameter from which the SFnumber/index may be inferred). This information may be useful in asituation in which the SF boundary (or SF number/index) of the UCell isnot aligned with the PCell (e.g., the floating-RRP) or in a situationwhere the UE directly detects the RRP start point (a specific preamble,synchronization signal, reference signal, or the like for identifyingthe RRP start point).

Start Symbol Position Information about UCell SF

This information may be signaled to indicate the interval between thestart OFDMA symbols of the PCell SF and the UCell SF having the same SFnumber/index or information for inferring the same, and/or thepositional relationship between the start OFDMA symbols of the PCell SFand the UCell SF having the same SF number/index. For example, thisinformation may indicate how far the start OFDMA symbols of the PCell SFand the UCell SF having the same SF number/index are spaced from eachother (e.g., the number of OFDMA symbols). In addition, this informationmay indicate whether the start OFDMA symbol of the UCell SF is locatedearlier or later than the start OFDMA symbol of the PCell SF having thesame SF number/index). This information may be useful in a situation inwhich the SF boundary (or the SF number/index) of the UCell is notaligned with that of the PCell (e.g., a situation of the floating-RRP).

rrp Index/Number

This information may be signaled to indicate the index (or number) forthe RRP (relative to, for example, the RRP). For example, the RRPindexes may be determined in a manner that RRP index 0 is determined forthe first RRP configured/set in the UCell, RRP index 1 is determined forthe second RRP configured/set in the UCell, and RRP index 2 isdetermined for the third RRP configured/set in the UCell in time order.

When RRP indexes are given, the UL channel/signal transmission relatedinformation and/or the DL channel/signal transmission relatedinformation in the UCell may be configured/defined based on the RRPindex and/or the SF index/number in the RRP. Here, the UL channel/signaltransmission related information includes, for example, PRACH preambletransmission timing, SRS transmission timing/period, PUSCHretransmission timing gap, and the like. The DL channel/signaltransmission related information may include, for example, asynchronization signal (e.g., PSS/SSS) transmission timing/period, ameasurement/tracking RS (e.g., CRS, Discovery RS) transmissiontiming/period, CSI-RS transmission timing/period, interferencemeasurement resource (i.e. CSI-IM or zero-power CSI-RS) configurationtiming/period, and the like.

(2) Determination of RRP Start SF in UCell

The following two schemes may be considered as methods for determiningthe start point (e.g., SF) of the RRP interval that is aperiodicallyconfigured on the UCell (from the perspective of the UE).

-   -   Alt S1: The time when a specific signal is detected on the UCell        is determined as the RRP start SF.

When a specific signal (hereinafter referred to as a UCell preamble) isconfigured to be transmitted only through a start portion (e.g., SF)within an RRP interval, the UE may directly perform a detectionoperation on the UCell preamble. The UE may determine the time when theUCell preamble is detected as the start point (e.g., SF) of the RRPinterval. The UCell preamble may be in the form of, for example, apreamble, a synchronization signal (e.g., PSS and/or SSS), a referencesignal (e.g., CRS), or the like.

-   -   Alt S2: The RRP start SF is implicitly determined from a        specific SF time of the PCell.

A specific (SF) time on the PCell, for example, an SF in which theRRP-cfg DCI is detected (or a time obtained by adding a specific SFoffset to the specific time) may be determined as the start point (e.g.SF) of the RRP interval. In this case, the UE may operateassuming/considering that (at least) the SF boundary of the UCell isaligned with that of the PCell. This scheme may be useful in a situationwhere there is no separate signal configuration for indicating thestarting point within the RRP interval).

When the start point of the RRP interval and the SF boundary of UCellare determined based on the above scheme or another scheme, thefollowing methods may be used to determine the SF number/index.

-   -   The SF number/index is determined through detection of the        attribute of a UCell preamble signal.

The mapping relationship between the attribute of the UCell preamblesignal and the SF number/index may be preset such that the attribute ofthe UCell preamble signal may be classified according to the SFnumber/index. Accordingly, the UE may determine the SF number/index ofthe SF including the UCell preamble signal in the RRP by detecting thesignal attribute of the UCell preamble. For the remaining SFs in theRRP, the corresponding SF number/index may be determined inconsideration of the relative time relationship with the correspondingpreamble SF. The attributes of the UCell preamble signal include, forexample, a sequence (pattern or type) constituting the preamble signal,and a resource (e.g., OFDMA/SC-FDMA symbol or RE) on which the preamblesignal is transmitted.

For example, it may be assumed that the preamble sequence (pattern) #0is mapped to the SF (number/index) #0 and the sequence #1 corresponds tothe SF #1, namely, when sequence #n is mapped to SF #n. It is assumedthat One RRP interval (length) is composed of 3 SFs, and the UCellpreamble is configured/transmitted in the RRP start SF. In this case,when sequence #5 is detected through the UCell preamble signal, the SFnumbers/indexes corresponding to the three SFs constituting the RRP maybe determined as SFs #5, #6, and #7 in time order.

-   -   The SF number/index is determined according to the SF overlap        portion between UCell and PCell.

The SF (number/index) corresponding to a PCell SF more overlapping theinterval of the UCell SF may be determined as the SF number/index of thecorresponding UCell SF. Equivalently, the SF number/index correspondingto a UCell SF may be determined depending on the slot in the overlappingPCell SF where the start point of the UCell SF is located. For example,the SF number/index of the UCell SF may be determined as SF #n when thestart point of the UCell SF is located in the first slot of theoverlapping PCell SF (e.g., SF #n) and as SF #(n+1) when the start pointof the UCell SF is located in the second slot of the overlapping PCellSF.

Alternatively, the SF number/index of the corresponding UCell SF may bedetermined to be Opt 1) an SF number/index corresponding to the PCell SFoverlapping at the end of the UCell SF or Opt 2) an SF number/indexcorresponding to the PCell SF overlapping at the start point of theUCell SF. In a situation of cross-CC scheduling, in consideration of thedecoding latency for the PDSCH scheduled in the UCell, the processingtime between PDSCH reception and HARQ-ACK transmission, and theprocessing time between the PUSCH transmitted through the UCell and ULgrant DCI transmission, and the like, the Opt 1 scheme may be applied ifall SFs in the RRP interval are configured as DL SFs and the Opt 2scheme may be applied if all SFs in the RRP interval are configured asUL SFs.

In the case of Opt 1, the SF number/index corresponding to the PCell SFmore overlapping the corresponding UCell SF, between 1) the PCell SFoverlapping with the end point of the UCell SF and 2) the PCell SFoverlapping with the previous/following point spaced by a specific timeoffset (e.g. X us) from the end point of the UCell SF, may be determinedas the SF number/index of the corresponding UCell SF. Similarly, in thecase of Opt 2, the SF number/index corresponding to the PCell SF moreoverlapping the corresponding UCell SF, between 1) the PCell SFoverlapping the start point of the UCell SF and 2) the PCell SFoverlapping the following/previous point spaced by a specific timeoffset (e.g. X usec) from the start point of the UCell SF, may bedetermined as the SF number/index of the corresponding UCell SF.

(3) UE Operation According to RRP Configuration/Setting

There are two cases in which the transmission structure of the RRP-cfgDCI (e.g. Alt D1 or D2) and the RRP start SF determining method (e.g.Alt S1 or S2) are combined. In each case, the following UE operationsmay be considered according to the result of RRP-cfg DCI detection.

Case 1: Alt D1 or D2+Alt S1

The UE may Opt 1) attempt to detect the UCell preamble from k (k=0, . .. ) SFs after the time at which RRP-cfg DCI detection succeeds(particularly, in case of Alt D1) or the time at which the UE performsthe RRP-cfg DCI detection operation, or Opt 2) always perform the UCellpreamble detection operation regardless of success/failure of RRP-cfgDCI detection or the detection cycle.

If the UE fails to detect the RRP-cfg DCI but succeeds in detecting theUCell preamble, the UE may operate on the assumption of only thepredetermined minimum RRP interval. This scheme may be useful in asituation in which the UE attempts UCell preamble detection based on thetime of RRP-cfg DCI detection operation (Opt 1) or at all times (Opt 2)regardless of whether RRP-cfg DCI detection is successful or not. On thecontrary, if the UE succeeds in detecting RRP-cfg DCI but fails todetect the UCell preamble, the UE may rely only on the detection of theDL/UL grant DCI for scheduling the data transmission in the UCell toconfigure the SF resources on the UCell, and perform DL/ULtransmission/reception only through the configured SF resources. Thisscheme may be useful in a situation in which the UE operates with the SFboundaries of the UCell and the PCell aligned.

Case 2: Alt D1 or D2+Alt S2

The UE may operate on the assumption that the RRP interval starts on theUCell after k (k=1, . . . ) SFs from the RRP-cfg DCI detection time. Atthis time, if the UE fails to detect RRP-cfg DCI, the UE may rely onlyon the detection of the DL/UL grant DCI for scheduling data transmissionin the UCell to configure the SF resources on the UCell, and performDL/UL transmission/reception only through the configured SF resources.

(4) UE Operation According to Floating-RRP Configuration

The RRP on the UCell may include a DL SF and be configured in the formof floating-RRP. In this case, there is a possibility that the timeinterval between the completion time of decoding of PDSCH transmittedthrough the UCell and the corresponding HARQ-ACK feedback transmissiontime in the PCell is much shorter than the existing time interval,depending on the positional relationship between the UCell SF and thePCell SF having the same SF number/index (in particular, in a case wherethe PCell SF is positioned ahead of the UCell SF by more than a certaininterval). In such a situation, in order to make it possible to processa given PDSCH signal and HARQ-ACK signal within the shortened timeinterval, the processing speed/capability of the UE may need to beimproved correspondingly, which may greatly increase UE complexitycompared to conventional cases.

Accordingly, the UE may determine/generate and transmit “NACK” as theHARQ-ACK response regardless of the result of PDSCH decoding, ortransmit no HARQ-ACK signal under situations/conditions given below.Alternatively, under the same situation/condition, the UE may feed backthe decoding result (e.g., ACK or NACK) for the remaining OFDMAsymbol(s) of the entire PDSCH reception signal except for some of thelast OFDMA symbol(s) of the signal (e.g., puncturing the correspondingOFDMA symbol(s)) as a HARQ-ACK response for the corresponding PDSCHreception under the same situations/conditions:

-   -   the time interval between (i) the UCell SF and (ii) the PCell SF        having the same SF number/index is greater than a specific value        (particularly, the PCell SF precedes the UCell SF);    -   the time interval between (i) the time of PDSCH signal reception        (completion) (in the UCell) and (ii) the corresponding time of        (start of) transmission of an HARQ-ACK signal (in the PCell) is        shorter than a specific value, or the time interval between (i)        the time of completion of PDSCH decoding and (ii) the time of        generation of the corresponding HARQ-ACK signal is shorter than        a specific value (i.e., PDSCH decoding is not completed until        the time when the HARQ-ACK response is to be determined).

Similarly, in the following situations/conditions, the UE mayomit/discard PUSCH transmission corresponding to the DCI or exclude thefirst few SC-FDMA symbol(s) of the entire (scheduled) PUSCH signal(e.g., performing puncturing on the corresponding symbol(s)) andtransmit the remaining SC-FDMA symbol(s):

-   -   the time interval between (i) the UCell SF and (ii) the PCell SF        having the same SF number/index is longer than a specific value        (particularly, the UCell SF is located before the PCell SF),    -   the time interval between (i) the time of UL grant DCI reception        (completion) (in the PCell) and the corresponding time of (start        of) PUSCH signal transmission (in the UCell) is shorter than a        specific threshold, or the time interval between (i) the time of        completion of UL grant DCI decoding and (ii) the corresponding        time of PUSCH signal generation is shorter than a specific        threshold value (i.e., the UL grant DCI decoding is not        completed until PUSCH signal generation is to be started).

(5) DL Power Allocation Method for RRP

In the case of the legacy LTE system, allocation of the DL signaltransmit power in the existing DL SF may be determined by the followingparameters.

-   -   P_R: CRS RE transmit power (linear average in [W])    -   P_A: A ratio of PDSCH RE transmit power in a transmission symbol        in which the CRS is not transmitted to CRS RE transmit power (in        [dB])    -   P_B: A ratio of PDSCH RE transmit power in a transmission symbol        in which CRS is transmitted to CRS RE transmit power (in [dB])    -   P_C: A ratio of PDSCH RE transmit power (in a transmission        symbol in which CRS is not transmitted) to CSI-RS RE transmit        power (in [dB])

Specifically, the eNB determines the DL transmit power for each RE. TheUE assumes that the CRS RS EPRE (Energy Per Resource Element) (i.e.,P_R) is constant over the entire DL BW and is constant over allsubframes until new CRS power information is received. The CRS RS EPREmay be inferred based on a parameter (e.g., referenceSignalPower)provided by higher layer (e.g., RRC) signaling. The ratio of the PDSCHEPRE to the CRS RS EPRE (i.e., PDSCH EPRE/CRS RS EPRE) is setdifferently considering the CRS distribution. For example, one of P_Aand P_B may be inferred and determined based on a parameter provided byhigher layer (e.g., RRC) signaling, and the other one of P_A and P_B maybe determined using the ratios therebetween. For example, P_A/P_B mayhave various values such as 1, 4/5, 3/5, and 2/5 depending on CRSdistribution (e.g., the number of antenna ports).

If the RRP interval configured on the UCell includes CRS transmission,allocation of the DL signal transmit power in the UCell RRP interval maybe performed based on the scheme above. Here, if path-loss measurementvia CRS receive power is not required in the UCell, definition/settingof P_R in the UCell may be omitted.

If the RRP interval configured on the UCell does not include CRStransmission or uses only the CSI-RS as a UE-common RS, allocation of DLsignal transmit power in the UCell RRP interval may be performed byreplacing the parameters of the conventional scheme with the parametersof Method 1/2 below. In this case, definition/configuration of P_R inthe UCell may be omitted if path loss measurement through the CSI-RSreceive power is not required in the UCell.

Method 1

-   -   P_R: CSI-RS RE transmit power    -   P_A: PDSCH RE transmit power in a symbol in which CSI-RS is not        transmitted relative to CSI-RS RE transmit power    -   P_B: PDSCH RE transmit power in a symbol in which CSI-RS is        transmitted relative to CSI-RS RE transmit power

Method 2

-   -   P_R: CSI-RS RE transmit power    -   P_A: PDSCH RE transmit power (in any symbol) relative to CSI-RS        RE transmit power

For the RRP configured on the UCell, considering that the channelenvironment and the interference influence may vary over time due to thenature of the unlicensed band (due to attempts to transmit signals fromother systems (e.g. Wi-Fi)), the values of P_R, P_A, P_B, and PCparameters in Method 0/1/2 may be independently configured in RRP (orRRP group) units or specific time duration units. These power allocationparameters may be signaled in a UE-common manner through a PDCCHconfigured/transmitted on the CSS of the PCell or a preamble signalconfigured/transmitted on the UCell, or may be UE-specifically signaledthrough a DL grant for scheduling data transmission in the Ucell or a ULgrant (for requesting/instructing aperiodic CSI reporting). Further, aplurality of possible combinations of the power allocation parameters(e.g., P_R, P_A, P_B, and P_C) may be preset via a higher layer signal(e.g., RRC signaling), and a parameter combination to be applied toUcell power allocation may be dynamically indicated via the specificsignal (e.g., the PDCCH, preamble or DL/UL grant).

Meanwhile, the conventional normal SCell is UE-specifically configured,but the SCell (i.e., UCell) operating in the unlicensed band may beconfigured in a UE-common manner. Therefore, it is also possible totransmit the entire system information about the UCell or a specificpart thereof through a specific broadcast signal (e.g., SIB (SystemInformation Block)) in the PCell.

The proposed methods of the present invention may not be limitedlyapplied to cells operating based on an aperiodic RRP configuration suchas LTE-U, and may be applied to a general cell operating based on thetransmission resource configuration as in legacy LTE in a similarmanner.

FIG. 14 illustrates a communication method according to an embodiment ofthe present invention.

Referring to FIG. 14 , a UE may configure a PCell of a licensed band andan SCell of an unlicensed band for an eNB (S1402). Then, the UE mayreceive resource configuration information (e.g., RRP-cfg DCI) about theSCell (i.e., UCell) through a PDCCH of the PCell (i.e., LCell) (S1404).Thereafter, the UE may configure a subframe set (e.g., RRP) within atemporary time period of the SCell (i.e., UCell) based on resourceconfiguration information (e.g., RRP-cfg DCI) (S1406). The UE may thenperform communication with the eNB using the subframe set (e.g., RRP)temporarily configured on the SCell (i.e., UCell). Here, for details ofthe RRP-cfg DCI and the RRP and the operations of the UE/eNB (e.g., HARQfeedback operation, power control operation, etc.), see the descriptionsgiven above.

FIG. 15 illustrates a BS and a UE of a wireless communication system,which are applicable to embodiments of the present invention.

Referring to FIG. 15 , the wireless communication system includes a BS110 and a UE 120. When the wireless communication system includes arelay, the BS or UE may be replaced by the relay.

The BS 110 includes a processor 112, a memory 114 and a radio frequency(RF) unit 116. The processor 112 may be configured to implement theprocedures and/or methods proposed by the present invention. The memory114 is connected to the processor 112 and stores information related tooperations of the processor 112. The RF unit 116 is connected to theprocessor 112 and transmits and/or receives an RF signal. The UE 120includes a processor 122, a memory 124 and an RF unit 126. The processor122 may be configured to implement the procedures and/or methodsproposed by the present invention. The memory 124 is connected to theprocessor 122 and stores information related to operations of theprocessor 122. The RF unit 126 is connected to the processor 122 andtransmits and/or receives an RF signal.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It will beobvious to those skilled in the art that claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present invention or included as anew claim by a subsequent amendment after the application is filed.

In the embodiments of the present invention, a description is madecentering on a data transmission and reception relationship among a BS,a relay, and an MS. In some cases, a specific operation described asperformed by the BS may be performed by an upper node of the BS. Namely,it is apparent that, in a network comprised of a plurality of networknodes including a BS, various operations performed for communicationwith an MS may be performed by the BS, or network nodes other than theBS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘NodeB’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc. The term‘UE’ may be replaced with the term ‘Mobile Station (MS)’, ‘MobileSubscriber Station (MSS)’, ‘mobile terminal’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

The embodiments of the present invention mentioned in the foregoingdescription may be applicable to various kinds of mobile communicationsystems.

What is claimed is:
 1. A base station (BS) configured to perform acommunication in a wireless communication system, the BS comprising: atleast one radio frequency (RF) unit; at least one processor; and atleast one computer memory operably coupled to the at least one processorand, when executed, causing the at least one processor to performoperations, wherein the operations include: transmitting a downlinkcontrol information (DCI) for a plurality of unlicensed frequency bands,wherein the DCI includes a plurality of information related with channeloccupancies of the plurality of unlicensed frequency bands; andperforming the communication in a contiguous time period of one of theplurality of unlicensed frequency bands, associated with the DCI,wherein the plurality of information have a one-to-one mapping with theplurality of unlicensed frequency bands, and each of the plurality ofinformation indicates whether a corresponding one of the plurality ofunlicensed frequency bands is available or not until an end of thecontiguous time period.
 2. The BS of claim 1, wherein the operationsfurther include transmitting a preamble signal, and wherein the startingindex of the contiguous time period is associated with a sequence indexof the preamble signal, and each sequence index is associated with anindex of a respective time unit.
 3. The BS of claim 2, wherein thestarting index of the contiguous time period is associated with aresource unit used for the reception of the preamble signal, and eachresource unit is associated with an index of a respective time unit. 4.The BS of claim 3, wherein the resource unit includes a symbol or aresource element.
 5. The BS of claim 1, wherein the contiguous timeperiod includes consecutive time units.
 6. A method of performing acommunication by a user equipment (UE) in a wireless communicationsystem, the method comprising: receiving a downlink control information(DCI) for a plurality of unlicensed frequency bands, wherein the DCIincludes a plurality of information related with channel occupancies ofthe plurality of unlicensed frequency bands; and performing thecommunication in a contiguous time period of one of the plurality ofunlicensed frequency bands, associated with the DCI, wherein theplurality of information have a one-to-one mapping with the plurality ofunlicensed frequency bands, and each of the plurality of informationindicates whether a corresponding one of the plurality of unlicensedfrequency bands is available or not until an end of the contiguous timeperiod.
 7. The method of claim 6, the method further comprising:transmitting a preamble signal, and wherein the starting index of thecontiguous time period is associated with a sequence index of thepreamble signal, and each sequence index is associated with an index ofa respective time unit.
 8. The method of claim 7, wherein the startingindex of the contiguous time period is associated with a resource unitused for the reception of the preamble signal, and each resource unit isassociated with an index of a respective time unit.
 9. The method ofclaim 8, wherein the resource unit includes a symbol or a resourceelement.
 10. The method of claim 6, wherein the contiguous time periodincludes consecutive time units.
 11. A user equipment (UE) configured toperform a communication in a wireless communication system, the UEcomprising: at least one radio frequency (RF) unit; at least oneprocessor; and at least one computer memory operably coupled to the atleast one processor and, when executed, causing the at least oneprocessor to perform operations, wherein the operations include:receiving a downlink control information (DCI) for a plurality ofunlicensed frequency bands, wherein the DCI includes a plurality ofinformation related with channel occupancies of the plurality ofunlicensed frequency bands; and performing the communication in acontiguous time period of one of the plurality of unlicensed frequencybands, associated with the DCI, wherein the plurality of informationhave a one-to-one mapping with the plurality of unlicensed frequencybands, and each of the plurality of information indicates whether acorresponding one of the plurality of unlicensed frequency bands isavailable or not until an end of the contiguous time period.
 12. The UEof claim 11, wherein the operations further include transmitting apreamble signal, and wherein the starting index of the contiguous timeperiod is associated with a sequence index of the preamble signal, andeach sequence index is associated with an index of a respective timeunit.
 13. The UE of claim 12, wherein the starting index of thecontiguous time period is associated with a resource unit used for thereception of the preamble signal, and each resource unit is associatedwith an index of a respective time unit.
 14. The UE of claim 13, whereinthe resource unit includes a symbol or a resource element.
 15. The UE ofclaim 11, wherein the contiguous time period includes consecutive timeunits.